Field of the Invention
The present invention relates to a radar-based fill level measurement device having a security device.
Background of the Invention
The current state of knowledge is as follows.
Radar-based fill level measurement devices having such a security device are known in the prior art, for example from U.S. Pat. No. 8,009,085 B2, and have a signal generator for the purpose of producing electromagnetic waves, and an antenna for the purpose of emitting the electromagnetic waves into a container, as well as for the purpose of receiving reflected electromagnetic waves out of the container, wherein the security device is suitably designed to verify the proper functioning of the radar-based fill level measurement device. The security devices demonstrated in the prior art have a reflector and an adjusting device for this purpose, said adjusting device being suitably designed to adjust the reflector at least between a first position in which it reflects the electromagnetic waves, and a second position in which it reflects the electromagnetic waves to a reduced degree.
The radar-based fill level measurement devices known in the prior art are generally used in containers which are generally constructed as tanks or silos for the purpose of storing various different materials. Foods, drinks, drugs, or fuels, by way of example, are stored in such tanks, such that a measurement of the fill level thereof must be carried out without contact. In the prior art, such contactless fill level measurement techniques are, by way of example, the radar-based fill level measurement device mentioned above, or an alternative ultrasound-based fill level measurement device. Radar-based fill level measurement devices are widely used due to their measurement precision and minimal susceptibility to failure.
The radar-based fill level measurement devices known in the prior art are generally installed in the upper region of a tank or silo via a flange, wherein the electronics are arranged outside, and the antenna of the radar-based fill level measurement device is arranged inside, of the housing. The antenna is suitably designed for the purpose of transmitting electromagnetic waves—meaning particularly a radar signal—in the direction of the fill material which is stored inside the container, and of receiving electromagnetic waves reflected by the material. The fill level inside the container can be determined based on the time difference between a transmission of the electromagnetic signal and the reception of the reflected electromagnetic signal.
For the purpose of verifying the proper functioning of the radar-based fill level measurement device, particularly to verify the proper functioning when the fill level is maximum, the same being relevant to safety, it is necessary to include a security device which makes it possible to determine the proper functioning when the fill level is at maximum. In the prior art, for this purpose, the practice of manually placing a reflector in the beam path of the radar-based fill level measurement device, during a security test, is known, to verify the functioning of the measurement device at the desired maximum fill level, even when the container fill level is lower—by bringing the reflector, when the fill level is lower, into the beam path of the radar-based fill level measurement device, and thereby generating a reflection corresponding to the maximum fill level.
In the devices known from the prior art, for this purpose it is necessary for an operator to manually place the reflector in the beam path of the radar-based fill level measurement device, wherein the operator must climb onto the container being monitored in order to operate the reflector. Because monitored containers are typically silos or tanks with heights up to 35 m, this presents a significant risk. In addition, it is considered disadvantageous that, for a security verification, every single container must be visited and the reflector manually operated.
The problem addressed by the present invention is that of removing the disadvantages known from the prior art, and of providing an advanced radar-based fill level measurement device which does not have these disadvantages.
This problem is addressed by a radar-based fill level measurement device having the features disclosed herein.